Coolant flow means utilizing tubing of dielectric material



Sept. 24, 1968 w. J. GRIFFIN 3,403,292

COOLAN'T FLOW MEANS UTILIZING TUBING OF DIELECTRIC MATERIAL Filed Sept.26, 1966 2 Sheets-Sheet 1 WHmH -gi I l Ill:

IIJHUH INVENTOR. 1 Walter J.Griffin Sept. 24, 1968 w. J. GRIFFIN3,403,292

COOLANT FLOW MEANS UTILIZING TUBING OF DIELECTRIC MATERIAL Filed Sept.26, 1966 2 Sheets-Sheet 2 INVENTOR. Woll)er J. Griffin United StatesPatent O 3,403,292 COOLANT FLOW MEANS UTILIZING TUBING OF DIELECTRICMATERIAL Walter J. Griflin, Sudbury, Mass, assignor, by mesneassignments, to the United States of America as represented by theSecretary of the Navy Filed Sept. 26, 1966, Ser. No. 582,474 7 Claims.(Cl. 315-50) ABSTRACT OF THE DISCLOSURE oil-seal flange.

This invention relates to electron discharge devices and, moreparticularly, to high power output devices in which cooling is requiredto permit increased high average power operation.

As high power levels are reached in the operation of amplifier tubessuch as the microwave crossfield amplifier tube, the tubes cathodeabsorbs energy from electrons which are returned by the interactionprocess. This backbombardment by electrons is relatively unimportant inlow power devices but becomes exceedingly important in higher powerdevices because the back-bombardment energy adds to the heating of thecathode as the operating power level is increased. Eventually thecathode is raised to such high temperatures that radiation cooling isineffective, resulting in melted or vaporized materials therein.

In the field, the melting and vaporization of cathode materials hasdefined an upper limit to the operating average power levels attainableby devices incorporating these tubes. In the laboratory, this powerlimitation has been avoided by causing liquid coolant to flow from openreceptacles through the cathode structure to remove heat in the same orsimilar manner as liquid coolants are used in many heated devices.

Several disadvantages are inherent in prior cathode cooling devices ofthe type mentioned, perhaps the most serious being the exposure ofpersonnel to a coolant which is at the same high voltage as the cathode.Although insulation may be provided along the coolant path between thecathode and the coolant source, there is no known device or method formaking the coolant lines and connections compatible with conventionaltube systems. In particular, where high voltage bushings are immersed ininsulating oil there is no known device or method for introducingcoolant fluid into the cathode structure through an oil chamber withouteffecting major alterations to the structure and chamber. The microwavecrossfield amplifier tube is an example of an important microwavecomponent which is increasing in use and requires cathode cooling meansnot available at the present state of the art.

One embodiment of the present invention solves the problem of mountinghigher powered microwave crossfield amplifier tubes and coolant linestherefor in conventionally oil-insulated systems by providing for safeand practical entrance and egress of the cathode coolant withoutsignificantly affecting normal high power output tube mountingarrangements.

Accordingly, it is an object of the present invention to provide a novelmethod of and means for applying coolant to the cathodes of high poweroutput devices.

Another object of the present invention is to provide means for coolingthe cathode structure of tubes operating at high average power such asmicrowave crossfield amplifier tubes without exposing personnel tolethal high voltages.

A further object of this invention is to provide a novel means of andmethod for entrance and egress of cathode coolant in high power outputdevices without significant change in conventional tube mountingstructure.

Other objects, advantages and novel features of the invention willbecome apparent from the following detailed description of the inventionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is an elevation view, partly cut away, of a power tube embodyingthe present invention; and

FIG. 2 is an enlarged view, in section, of the novel features of theinvention in relation to the structure of a conventional power tube.

Referring now to the drawings wherein like reference numerals designateidentical or corresponding parts throughout the views, and moreparticularly to FIG. 1, a high power output tube such as Amplitron tube11 is shown supported on a chamber 12 which contains a pulse transformer13 and is filled with insulating oil as indicated at 14. Tube 11 is amicrowave crossfield amplifier tube having a cathode 15 located along anaxis 16 which is concentric with the tube anode 17. Anode cooling is nota part of this application but is effected through an inlet 18, tubes 19and an outlet 20, all of which are outside of chamber 12 and, therefore,present no problem such as that posed in providing cathode cooling.

Excessive cathode heating is controlled by removing the excess heat fromthe cathode via a liquid coolant which is forced to flow from a coolantsource, not shown, through conduit means which include an inlet tube 23and an outlet tube 24, both of which are disposed entirely Withinchamber 12 and its sealing flange 25. Since, in the embodimentillustrated, chamber 12 is hermetically sealed at flange 25, a pair ofcoolant lines 27 and 28 are connected to passages through the oil-sealflange 25 in fittings 29 and 30, respectively, so as to maintain theintegrity of the hermetically sealed chamber. In oil-filled chamber 12,high voltage exists at 32 and ground potential at 33, these beingseparated by an insulator 34. Inlet and outlet tubes 23 and 24,respectively, are nonconducting and flexible and preferably are made ofhigh dielectric strength tubing. Conventional sealing components, suchas externally threaded connections 36, nuts 37 and adapters 38, are usedat the ends of tubes 23 and 24.

FIG. 2 shows the cathode structure in enlarged cross section ascomprising an outer conductive sleeve 40 to which a cathode emitter 41is attached and a centrally disposed inner sleeve 42 which provides aninlet passage 44 for coolant fluid. An outlet passage 45 is formedbetween outer conductive tube 40 and inner sleeve 42. High voltageapplied at the lower end of the structure to a connector 48 is conductedthrough inlet cap 49, lower plate 50, collar 51 and upper plate 52 tothe lower end 55 of insulator 32. Sleeve 42 and cap 49 are attached tolower plate in sealing engagement therewith, plate 50 also receiving insealing engagement an outlet cap 56. Cap 49 provides a plenum for intakecoolant while collar 51 and cap 56 form a plenum 57 for dischargecoolant. Plate 50 supports and centers inlet sleeve 42 in the devicealthough additional centering means, not shown, may be included adjacentthe end of the tube remote from plate 50 to insure that sleeve 42remains in the desired position. Outer sleeve 40 receives support andcentering from an insert 58 in upper plate 52. A central support membersuch as pole piece 59 is provided which is maintained at groundpotential and spaced an appropriate distance from the high voltage ofcathode support sleeve 40. A pair of end hats 60 and 61 are positionedon and supported by the cathode for the purpose of shaping electricalfields in the device.

On the exposed side 65 of sealing flange 25, fittings 30 are secured insealing engagement on a pair of externally threaded tube stubs 66 and67, respectively. A venting chamber 70 is formed by a flanged plate 72and flange 25. Tube stubs 66 and 67 pass through venting chamber 70 topreserve the integrity of the cooling system. The stubs 66 and 67connect fittings 29 and 3G to tubes 23 and 24, respectively. Flange 72is perforated as shownat 73 to provide communication between housing 12and chamber 70. Flange 25 has a hole, not shown, in its exposed side 65to receive a vent fitting, not shown, permitting air trapped in housing12 to be vented therefrom after the housing has been scaled.

A source of coolant, not shown, and pumping means, not shown, completethe cooling system. Since the entire cooling system is electricallygrounded at flange 25, there is no danger of exposing personnel tolethal voltages. Coolant enters through line 27, fitting 29, stub 66 andinlet tube 23, thence is directed into inlet cap 49 and through passage44 in inner sleeve 42 to the region of cathode emitter 41. The returnflow is directed downward past the cathode emitter region and throughpassage 45 to plenum 57 between plates 50 and 52, thence through cap 56,outlet tube 24, stub 67, fitting 30 and line 28, to a heat exchanger,not shown, or directly to the coolant source.

Coolant lines 27 and 28 and tubes 23 and 24 preferably are made offlexible high strength dielectric material to provide for differentialexpansion and resistance to impact damage. Negligible leakage currentlosses occur in such lines, and their composition is selected forchemical inertness to the oils and coolant fluids encountered. Thematerial of the lines further has the property of being capable offorming a seal with the metal fittings and terminal connections of thedevice.

By having the coolant path traverse oil-seal flange 25, the conventionalhigh voltage bushing oil seal may be made in the usual manner therebyavoiding a necessity for installing separate oil seals in additionalopenings in chamber 12. A positive electrical ground of the coolant isprovided by a ground connection 74 at the oil-seal flange.

There is thus provided a safe, simple method of and means for removingexcess heat from a cathode structure during high voltage operation. Theinvention is readily adaptable for use in other tube types as well as inforeseeable future high power tube devices and should make possibleincreased average power ratings therein.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. In a microwave crossfield amplifier device having an isolated highvoltage connection, the combination therewith of:

means for cooling at least a non-isolated portion of said device; saidcooling means including a coolant source disposed externally of theisolated portion of said device;

said cooling means further including a coolant fluid and conduit meansfor conducting said fluid through said device; and

said conduit means having inlet and outlet connections to saidnon-isolated portion of the device disposed in the isolated portionthereof.

2. The device of claim 1 wherein said high voltage connection isdisposed in a chamber;

said chamber being filled with insulating oil and sealed;

and

said non-isolated portion of the device includes the cathode thereofwhereby coolant fluid is introduced into the device and exited therefromthrough conduit means which are disposed at least partly within theinsulating oil in said chamber.

3. The device of claim 1 wherein said chamber is sealed by a sealingflange; and

said conduit means are admitted into the chamber through said sealingflange.

4. The device of claim 3 wherein said conduit means includes an inletsection and an outlet section disposed within said chamber;

said inlet and outlet sections composed of flexible nonconductingmaterial.

5. The device of claim 4 wherein said conduit means further includes acentrally disposed inlet passage extending through said flange to apoint beyond said cathode; and

an outer return passage concentrically disposed about the inlet passageand terminating Within said chamber.

6. The device of claim 5 wherein said crossfield microwave amplifierincludes a non-conducting central support member attached to saidflange;

said support member disposed externally of said chamber;

a high voltage connector disposed within said chamber remote from saidcentral support member for conducting high voltage thereinto;

passage forming means connecting said high voltage connector and saidcathode; and

insulating means disposed in said chamber concentrically spaced about atleast a portion of said passage forming means.

7. The device of claim 6 and further including a centrally disposedinner elongated sleeve extending from a position adjacent said highvoltage connector to a point beyond said cathode;

an outer sleeve concentrically disposed about and spaced from said innersleeve;

said passage forming means forming a plenum at the end of said outersleeve;

said plenum communicating with said outlet section;

said outer sleeve extending beyond said inner sleeve in the vicinity ofsaid cathode to permit intercommunication of said inlet and said outerpassages so that coolant fluid entering through said inlet section willtraverse said inner sleeve and thence said outer passage past saidcathode to said plenum and out through said outlet section.

References Cited UNITED STATES PATENTS 2,544,664 3/1951 Garner et a1.313-32 X 2,546,773 3/1951-=Nelson 315- X 2,574,562 11/1951 Hansell313-32 X 2,768,329 10/1956 Smith 313-32 X 2,787,730 4/1957 Berghaos etal 315-50 X JAMES W. LAWRENCE, Primary Examiner.

C. R. CAMPBELL, Assistant Examiner.

